LordViperion
Of course, any good audio recording program. Record your voice with a mic and change the pitch of it, add reverbs, flangers and effects to change your voice.
If you dont want to record your voice you can try FL Studio, it comes with a plugin that makes audio from a text. You have a few different voices by default, as robotic, old man, etc. Is it not enough, you can modify pitch, add reverbs, etc.
(Rigth click on any pad to see this menu)
I hope this help you